Device and method for the generation of a double or multiple spot in laser material processing

ABSTRACT

The invention relates to a device and a method for generating a multiple spot during laser material processing. According to the present invention, the power distribution is selected by pushing at least a first mirror into the laser beam. The light beam always falls on only one side of the mirror, so that the mirror can be produced easily and economically.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to German Patent Application No.DE 10 2019 108 681.7 filed on Apr. 3, 2019. The aforementionedapplication is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a device and a method for generating a multiplespot in laser material processing.

Brief Description of the Related Art

In laser material processing of metals or other materials, it is oftendesirable to be able to use a double spot or even multiple spots. Togenerate such spots different solutions are known from the state of theart.

Published German Patent Application No. DE 199 61 918 A1 describes amethod and a device for laser material processing with at least twolaser beam foci, which are imaged onto the workpiece to be processed,wherein a double focus is generated from a single focus of a laser beamby using refractive elements in a variable focus geometry, whereindistance and intensity between the foci can be freely selected. Thetechnical solution of this document is based on refractive elements,wherein in practice the usable power is limited to about 10 kW.

Published German Patent Application No. DE 402 42 99A1 teaches a devicefor focusing a light beam in at least two focal points with a mirrorelement which splits the light beam into a number of partial beamscorresponding to the number of focal points, wherein the mirror elementhas a number of mirror surfaces corresponding at least to the number offocal points and wherein the mirror element is movable relative to theincident light beam to vary the beam intensity in the individual focalpoints and the distance between the individual focal points. The systemtherefore has at least two mirrors for a double focus. The first concavemirror focuses a collimated laser beam. Between this mirror and thefocus there is a second mirror with two different mirror surfaces thathave an angle unequal to 0°. By varying the position of the secondmirror along or perpendicular to the optical axis, the intensity andposition of the two spots can be adjusted. A major disadvantage of thisinvention is that the distance between the second mirror and theworkpiece depends on the desired distance between the two spots. Duringthe laser material processing, droplets, metal vapors etc. are producedwhich limit the service life of the optics. A protective glass isnormally used for this purpose, which must be resistant enough towithstand a process operation. For an acceptable lifetime a geometricaldistance to the process, i.e. to the focus, is required. Furtherdisadvantages of the teaching of this document are the lack ofadjustment possibilities to be able to adjust the intensities andpositions of more than two spots independently of each other and thecomplexity of the second mirror, especially with regard to the coatingto the line where the two optical surfaces meet. The surface there hasan extremely small radius of curvature which, in combination with themechanical stresses inherent in the coating, has a strongly negativeeffect on the yield during production.

A complex mirror is avoided with the system from the publishedInternational Application No. WO 98/51442 A1. A first mirror deflectsthe laser beam, but according to this document, the beam hits twodifferent mirrors subsequently. The power distribution is adjusted hereby means of the vertical position of the first mirror. The position ofthe two spots can be changed by moving the other two mirrorshorizontally. However, even with this system it is still difficult toadjust the power in more than two spots independently. A bigger problemis that there is a gap between the other two mirrors. This isdisadvantageous for the application of the described system for highlaser power, because the gap will always be within the laser beam.

The problem of a gap is reduced by the teaching of the published ChineseUtility Model Np. CN 205764433 U by arranging mirrors directly next toeach other. A distance between two or three different spots is adjustedby tilting the corresponding mirrors. In principle, this design islimited to a maximum of three spots and the power would only beadjustable independently of each other with two spots.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is thereforeto enable the generation of a double or multiple spot with a lasermaterial processing optic for a power of at least 10 kW. Both, theposition and the power in the different spots should be adjustable.

The present invention provides a device for variable beam shaping of alight beam, comprising:

-   -   a. an entry aperture with an entry cross-section and with an        entry axis which passes centrally through the entry aperture, a        continuation of the entry cross-section along the entry axis        defining a free propagation volume;    -   b. a collimation optics arranged between entrance aperture and        an arrangement of mirrors;    -   c. the arrangement of mirrors comprising at least        -   i. a first mirror, the first mirror having a reflecting            surface only on a side facing the laser beam and being            arranged at least partially in a collimated laser beam for            re-reflection of a partial beam;        -   ii. a second mirror with a reflecting surface in the            direction of the reflecting surface of the first mirror to            deflect the reflected partial beam of the collimated laser            beam;        -   iii. a third mirror comprising a reflecting surface in the            direction of the second mirror to reflect the reflected            partial beam of the collimated laser beam back next to the            unreflected partial beam of the collimated laser beam;    -   d. a displacement device connected to at least one mirror of the        array of mirrors to move it into the undivided collimated laser        beam;    -   e. an angle adjusting device connected to at least one mirror of        the array of mirrors for its rotation; and    -   f. focusing optics arranged behind the third mirror for focusing        the reflected partial beam of the laser beam and the unreflected        partial beam of the collimated laser beam with at least one        double focus.

In a further aspect of the invention, the displacement device may beconnected to the first mirror.

Furthermore, an embodiment is provided in which the angle adjustingdevice can be connected to the second mirror.

Furthermore, in the arrangement of mirrors, a further mirror can beplaced between the first and second mirror and the mirrors can now benamed as follows

-   -   i. a first mirror, the first mirror having a reflecting surface        only on a side facing the collimated laser beam;    -   ii. a second mirror with a reflecting surface in the direction        of the first mirror to deflect the reflected partial beam of the        collimated laser beam;    -   iii. a fourth mirror comprising a reflecting surface towards the        second mirror for redirecting the reflected partial beam of the        collimated laser beam;    -   iv. a third mirror comprising a reflecting surface in the        direction of the fourth mirror to reflect the reflected partial        beam of the laser beam from the fourth mirror as well as the        unreflected partial beam of the collimated laser beam;        wherein the reflecting surfaces of the first and second mirrors        are arranged parallel to each other, the second or fourth mirror        is connected to the angle adjusting device for its rotation, and        the first and third mirrors are connected to the displacement        device and are movable therewith in the direction of reflection        of the partial beam of the collimated laser beam.

It may also be provided that a first and a third mirror are connected tothe displacement device so that they are movable transversely to thedirection of deflection of the collimated partial beam of the laserbeam.

If the device is further designed, the arrangement may comprise twofurther mirrors with which a second partial beam of the collimated laserbeam is reflected, the two further mirrors being named as follows,

-   -   a. a fifth mirror arranged adjacent to the first mirror for        reflecting a second partial beam of the collimated laser beam        onto the second mirror, and    -   b. a sixth mirror arranged adjacent to the third mirror for        reflecting the second reflected partial beam of the collimated        laser beam again adjacent to the unreflected partial beam of the        collimated laser beam, the fifth and sixth mirrors being movable        transversely to the deflection direction of the collimated        partial beam of the laser beam by means of a connection with a        second shifting device.

In the aforementioned embodiment, the second or fourth mirror may bedivided and the at least two parts may be independently adjustable.

In a further embodiment of the device according to the invention, thefirst and third mirrors can be arranged one behind the other, partiallyoverlapping, in such a way that they each partially reflect thecollimated laser beam onto the second mirror, the first mirror can bemoved into or out of the collimated laser beam at an angle to the beamdirection of the collimated laser beam by means of the displacementdevice, and the third mirror is connected to the angle adjustment devicein order to be able to rotate it.

It is further provided that the arrangement of mirrors comprises fourmirrors, wherein the first mirror is arranged to reflect a partial beamof the collimated laser beam to the second mirror, the third mirror isarranged partially overlapping behind the first mirror to redirect apartial beam of the collimated laser beam to the fourth mirror, and thesecond and fourth mirrors are arranged partially overlapping one behindthe other, in that they each deflect the reflected partial beam of thecollimated laser beam onto the focusing optics, the first and fourthmirrors being connected to a displacement device in order to move thelatter into or out of the collimated laser beam at an angle to the beamdirection of the collimated laser beam, and the second or third mirrorbeing connected to an angle adjustment device in order to be able torotate the latter.

Furthermore, in one version, the first and fourth mirrors can bearranged displaceable at right angles to the direction of deflection ofthe partial beam of the laser beam.

The present invention further relates to a method for generating amultiple spot in laser material processing, comprising the steps

-   -   a. Collimation of a divergent laser beam by means of collimation        optics;    -   b. Displacement of at least a first mirror in a part of the        collimated laser beam by a displacement device;    -   c. Reflecting a partial beam of the collimated laser beam        through the first mirror by means of a reflecting surface onto        the reflecting surface of a second mirror;    -   d. Reflecting the partial beam of the collimated laser beam        through the second mirror by means of a reflecting surface onto        the reflecting surface of a third mirror;    -   e. Reflection of the partial beam of the collimated laser beam        by the third mirror next to the unreflected partial beam of the        collimated laser beam;    -   f. Creating a difference angle between the reflected and the        unreflected partial beam by rotating at least one of the        mirrors;    -   g. Focusing of reflected and unreflected partial beam of the        collimated laser beam by means of focusing optics;    -   h. Imaging a beam focus with at least a double focus on a        workpiece to be processed.

The method can also be designed in such a way that four mirrors are usedto create a double focus.

Furthermore, the method may include the step of using a fifth and sixthmirror to generate an additional focus.

In a further embodiment of the method according to the invention, thedisplacement device can displace at least one mirror at an angle to thebeam axis of the collimated laser beam and/or transversely to thedirection of deflection of the partial beam of the collimated laserbeam.

Furthermore, the power ratio between reflected and non-reflectedcollimated laser beam can be set or adjusted by the displacement deviceby changing the dimension of the area of the reflecting surface of oneof the shifted mirrors in the collimated laser beam.

Still other aspects, features, and advantages of the present inventionare readily apparent from the following detailed description, simply byillustrating a preferable embodiments and implementations. The presentinvention is also capable of other and different embodiments and itsseveral details can be modified in various obvious respects, all withoutdeparting from the spirit and scope of the present invention.Accordingly, the drawings and descriptions are to be regarded asillustrative in nature, and not as restrictive. Additional objects andadvantages of the invention will be set forth in part in the descriptionwhich follows and in part will be obvious from the description, or maybe learned by practice of the invention

BRIEF DESCRIPTION OF THE FIGURES

The invention will be described based on figures. It will be understoodthat the embodiments and aspects of the invention described in thefigures are only examples and do not limit the protective scope of theclaims in any way. The invention is defined by the claims and theirequivalents. It will be understood that features of one aspect orembodiment of the invention can be combined with a feature of adifferent aspect or aspects of other embodiments of the invention, inwhich:

FIG. 1 shows an embodiment with four mirrors, where two mirrors aremovable in the direction of the deflection of the axis of the laserbeam.

FIG. 2 shows an embodiment with four mirrors, where two mirrors aremovable transversely to the direction of deflection of the axis of thelaser beam.

FIG. 3 shows an embodiment with six mirrors, where two mirrors can bemoved twice transversely to the direction of deflection of the axis ofthe laser beam.

FIG. 4 shows an embodiment with three mirrors, two of which can be movedtransversely to the direction of deflection of the axis of the laserbeam.

FIG. 5 shows an embodiment with three mirrors, where one mirror ismovable in the direction of the deflection of the axis of the laserbeam.

FIG. 6 shows an embodiment with four mirrors, whereby two mirrors can bemoved parallel to the direction of deflection of the axis of the laserbeam.

FIG. 7 shows an embodiment with four mirrors, where two mirrors can bemoved transversely to the direction of deflection of the axis of thelaser beam.

FIG. 8 shows an embodiment with four mirrors, whereby four mirrors canbe moved in the direction of the deflection of the axis of the laserbeam.

FIG. 9 shows an embodiment with three mirrors, whereby three mirrors canbe moved in the direction of the deflection of the axis of the laserbeam.

FIG. 10 shows an embodiment with three mirrors, where two mirrors aremovable in the direction of the deflection of the axis of the laserbeam.

DETAILED DESCRIPTION OF THE INVENTION

The previously formulated problem of the invention is solved by thefeatures of the independent claims. The dependent claims cover furtherspecific embodiments of the invention.

The invention provides a device capable of producing at least one doublespot. According to the present invention, the power distribution isselected by pushing at least a first mirror into the laser beam. Therebythe light beam always falls on only one side of the mirror, so that themirror can be produced easily and economically. The resulting(reflected) partial beams of the laser beam are mirrored via additionalmirrors in such a way that they are again reflected next to thenon-mirrored (direct) part of the laser beam. The total diameter of therecombined partial beams (mirrored and direct) is kept as small aspossible, so that subsequent optical systems can be as small aspossible. A raw beam diameter between 20-50 mm is only increased by max.1 mm in the present invention. The solution is both a cost-effectivesolution and a long service life of the protective glass.

FIG. 1 shows an embodiment in which a first mirror 21 with a mirrorsurface 25 and a first side surface 26 and first and second edges 27, 28of the mirror and a third mirror 23 can be moved together in thedirection of deflection of the partial beam of the laser beam. Surface26 can be completely in the shadow of surface 25 and therefore need notbe a mirror surface, which is an advantage of the invention.Furthermore, the angle between surface 25 and 26 need not be exactly90°. In the present invention, edge 27 is ultimately the only mirroredge of the structure that lies in the laser beam, which is also anadvantage with respect to the requirements for the manufacture of themirrors. The mirrors are displaced by means of a displacement device 30along the displacement axis 31, whereby the displacement causes a changein the power distribution between the two partial beams and accordinglyalso between the two spots on the workpiece.

A divergent light beam 97 emerges from an optical fiber 80 with a fibertip 81. This is collimated by the collimating optics 85 and passesthrough an entrance aperture 12 of the device according to the invention10. Arrow 90 indicates the beam direction of the now collimated lightbeam.

The partial beam of the laser beam reflected by the mirror surface 25first mirror 21 hits the second mirror 22, from which the partial beamof the laser beam is reflected to the fourth mirror 24, which directsthe partial beam to the third mirror 23. This in turn deflects thepartial beam of the laser beam so that this reflected part of the laserbeam now hits the focusing optics 87 next to the direct partial beam ofthe laser beam, from which a focused light beam 98 with a double beamfocus 99 emerges.

At least one of the existing deflecting mirrors must be connected to anangle adjustment device so that the mirror can be rotated to create amultiple spot. In FIG. 1, the fourth mirror 24 is connected to an angleadjuster 40, so that the reflected beam of the laser beam can be tiltedby the difference angle 77. By tilting a mirror, a small angle iscreated between the two partial beams (direct and reflected), so thatafter focusing through a focusing lens, they hit different positions onthe workpiece (double focus).

An alternative embodiment of the present invention is shown in FIG. 2.This design also comprises four mirrors which are arranged in acollimated laser beam. Of course, it is also possible to adjust thelight distribution by moving the mirrors in another direction, seeFIG. 1. Alternatively, other mirrors can be moved or tilted, or the fourmirrors can be arranged in such a way that an offset in the beam results(indicated by the double arrows).

In FIG. 2, the displacement of two mirrors is performed transversely tothe deflection of part of the laser beam, which is indicated by the twopoints enclosed by a circle, which are the axes on which the mirrors aredisplaced. Also, in the version in FIG. 2 at least one mirror must berotated or tilted (double arrow) to create at least one double spot.

A third adjustable spot can be obtained by adding additional mirrors. Anexample of this is shown in FIG. 3, where an additional pair of mirrorsenters the laser beam from the other (opposite) side. By tilting the twoparts of mirror 4 (not shown) independently, the distances between thethree spots can be adjusted independently.

Another possible embodiment of the present invention is shown in FIG. 4.The first mirror 21 deflects a part of the laser radiation away from theoptical axis of the laser beam. By moving mirror 21 in FIG. 4 in avertical axis for display (circle with a dot as axis transverse to thebeam direction), the fraction of the deflected laser light can beadjusted. By means of mirrors 22 and 23, this partial beam is againguided next to the non-deflected (direct) part of the laser light, sothat both partial beams can be focused on the workpiece through the samelens. The second mirror 22 can be rotated (double arrow), so that twospots are created on the workpiece, depending on the set angle of mirror22. In this version, mirror 23 is moved together with mirror 21, butthis does not necessarily have to be the case.

Another version is shown in FIG. 5. Here the power distribution isachieved by inserting the laser beam of the first mirror 21 in thedirection of the double arrow, i.e. in the direction of the deflection.However, here the laser light, which is not decoupled, is slightlytilted by means of the third mirror 23. Both beams then hit the secondmirror 22, which guides the partial beams of the laser beam towards thefocusing lens. The design shown in FIG. 5 is cost-effective due to thesmall number of relatively small mirrors.

Furthermore, it is possible to move the mirrors not perpendicular to thelaser beam, but rather diagonally to it, as shown in FIG. 6 as anexample with respect to the first mirror 21 and fourth mirror 24. Thesecond mirror 22 can be tilted or rotated to adjust the distance of thedouble focus. FIG. 7 shows a variant of the illustration in FIG. 6,where the first and fourth mirror 21, 24 can additionally be moved intothe collimated laser beam transversely to the laser beam direction(point with circle as axis). In principle, the displacement or tiltingis not limited to individual mirrors, as shown in FIG. 8 as an exampleand whose direction of movement is indicated by the double arrows.

A much shorter version of the present invention is shown in FIG. 9.Here, the first mirror 21 and the third mirror 23 are moved togetherwith the laser beam, either vertically (FIG. 9) or diagonally (FIG. 10).For this purpose, the first mirror 21 is also slightly tilted so thatthe two partial beams are focused on different positions on theworkpiece. The vertical distance between the first mirror 21 and thethird mirror 23 is selected in such a way that for each possible tiltingof mirror 21 there is no vertical gap between these two mirrors. Thismeans that each laser light beam falls on either mirror 21 or mirror 23.

With e.g. the design shown in FIG. 9, the second mirror can also beomitted, which means that the laser material processing head has a 90°angle and is no longer linear.

The above description of preferred embodiments of the invention has beengiven for the purposes of illustration and description. It is notintended to be exhaustive or to limit the invention precisely to thedisclosed form. Modifications and variations are possible in view of theabove teaching or can be obtained from the practice of the invention.The embodiment has been chosen and described to explain the principlesof the invention and its practical application in order to enable theperson skilled in the art to use the invention in various embodimentssuitable for the specific intended use. It is intended that the scope ofthe invention is defined by the attached claims and their equivalents.The entirety of each of the above documents is incorporated by referenceherein.

REFERENCE NUMERALS

-   10 Beam forming device-   11 Entry axis-   12 Entry aperture-   13 Entry cross section-   14 Propagation volume-   15 first partial section-   16 second section-   18 Exit aperture-   21 first mirror-   22 second mirror-   23 third mirror-   24 fourth mirror-   25 Mirror surface of the first mirror-   26 first lateral surface of the first mirror-   27 first edge of the first mirror-   28 second edge of the first mirror-   29 second lateral surface of the first mirror-   30 Displacement device-   31 Displacement axis-   35 fifth mirror-   36 sixth mirror-   40 Winkelstellvorrichtung-   41 Axis of rotation-   55 first partial axis-   56 Section of the first sub-axis-   57 further section of the first sub-axis-   66 second sub-axis-   67 further section of the second sub-axis-   71 first exit axis-   72 second outlet axis-   77 Difference angle-   80 Optical fiber-   81 Fiber Tip-   85 Collimation optics-   87 Focusing optics-   90 Light beam-   91 first sub-beam-   92 second partial beam-   97 divergent beam-   98 focused beam-   99 Beam focus

What is claimed is:
 1. A device for variable beam shaping of a lightbeam, comprising: a. an entry aperture with an entry cross-section andwith an entry axis which passes centrally through the entry aperture, acontinuation of the entry cross-section along the entry axis defining afree propagation volume; b. a collimation optics arranged betweenentrance aperture and an arrangement of mirrors; c. the arrangement ofmirrors comprising at least i. a first mirror, the first mirror having areflecting surface only on a side facing the laser beam and beingarranged at least partially in a collimated laser beam for re-reflectionof a partial beam; ii. a second mirror with a reflecting surface in thedirection of the reflecting surface of the first mirror to deflect thereflected partial beam of the collimated laser beam; iii. a third mirrorcomprising a reflecting surface in the direction of the second mirror toreflect the reflected partial beam of the collimated laser beam backnext to the unreflected partial beam of the collimated laser beam; d. adisplacement device connected to at least one mirror of the array ofmirrors to move it into the undivided collimated laser beam; e. an angleadjusting device connected to at least one mirror of the array ofmirrors for its rotation; and f. focusing optics arranged behind thethird mirror for focusing the reflected partial beam of the laser beamand the unreflected partial beam of the collimated laser beam with atleast one double focus.
 2. The device of claim 1, wherein thedisplacement device is connected to the first mirror.
 3. The device ofclaim 1, wherein the angle adjusting device is connected to the secondmirror.
 4. The device of claim 1, wherein in the arrangement of mirrors,a further mirror can be placed between the first and second mirror andthe mirrors can now be named as follows i. a first mirror, the firstmirror having a reflecting surface only on a side facing the collimatedlaser beam; ii. a second mirror with a reflecting surface in thedirection of the first mirror to deflect the reflected partial beam ofthe collimated laser beam; iii. a fourth mirror comprising a reflectingsurface towards the second mirror for redirecting the reflected partialbeam of the collimated laser beam; iv. a third mirror comprising areflecting surface in the direction of the fourth mirror to reflect thereflected partial beam of the laser beam from the fourth mirror as wellas the unreflected partial beam of the collimated laser beam; whereinthe reflecting surfaces of the first and second mirrors are arrangedparallel to each other, the second or fourth mirror is connected to theangle adjusting device for its rotation, and the first and third mirrorsare connected to the displacement device and are movable therewith inthe direction of reflection of the partial beam of the collimated laserbeam.
 5. The device of claim 4, wherein first and a third mirror areconnected to the displacement device so that they are movabletransversely to the direction of deflection of the collimated partialbeam of the laser beam.
 6. The device of claim 1, wherein thearrangement comprises two further mirrors with which a second partialbeam of the collimated laser beam is reflected, the two further mirrorsbeing named as follows, a. a fifth mirror arranged adjacent to the firstmirror for reflecting a second partial beam of the collimated laser beamonto the second mirror, and b. a sixth mirror arranged adjacent to thethird mirror for reflecting the second reflected partial beam of thecollimated laser beam again adjacent to the unreflected partial beam ofthe collimated laser beam, the fifth and sixth mirrors being movabletransversely to the deflection direction of the collimated partial beamof the laser beam by means of a connection with a second shiftingdevice.
 7. The device of claim 6, wherein second or fourth mirror aredivided and the at least two parts may be independently adjustable. 8.The device of claim 1, wherein first and third mirrors can be arrangedone behind the other, partially overlapping, in such a way that theyeach partially reflect the collimated laser beam onto the second mirror,the first mirror can be moved into or out of the collimated laser beamat an angle to the beam direction of the collimated laser beam by meansof the displacement device, and the third mirror is connected to theangle adjustment device in order to be able to rotate it.
 9. The deviceof claim 1, wherein the arrangement of mirrors comprises four mirrors,wherein the first mirror is arranged to reflect a partial beam of thecollimated laser beam to the second mirror, the third mirror is arrangedpartially overlapping behind the first mirror to redirect a partial beamof the collimated laser beam to the fourth mirror, and the second andfourth mirrors are arranged partially overlapping one behind the other,in that they each deflect the reflected partial beam of the collimatedlaser beam onto the focusing optics, the first and fourth mirrors beingconnected to a displacement device in order to move the latter into orout of the collimated laser beam at an angle to the beam direction ofthe collimated laser beam, and the second or third mirror beingconnected to an angle adjustment device in order to be able to rotatethe latter.
 10. The device of claim 9, wherein first and fourth mirrorscan be arranged displaceable at right angles to the direction ofdeflection of the partial beam of the laser beam.
 11. A method forgenerating a multiple spot in laser material processing, comprising thesteps a. Collimation of a divergent laser beam by means of collimationoptics; b. Displacement of at least a first mirror in a part of thecollimated laser beam by a displacement device; c. Reflecting a partialbeam of the collimated laser beam through the first mirror by means of areflecting surface onto the reflecting surface of a second mirror; d.Reflecting the partial beam of the collimated laser beam through thesecond mirror by means of a reflecting surface onto the reflectingsurface of a third mirror; e. Reflection of the partial beam of thecollimated laser beam by the third mirror next to the unreflectedpartial beam of the collimated laser beam; f. Creating a differenceangle between the reflected and the unreflected partial beam by rotatingat least one of the mirrors; g. Focusing of reflected and unreflectedpartial beam of the collimated laser beam by means of focusing optics;h. Imaging a beam focus with at least a double focus on a workpiece tobe processed.
 12. The method of claim 11, comprising the step of usingfour mirrors to create a double focus.
 13. The method of claim 11,comprising the step of using a fifth and sixth mirror to generate anadditional focus.
 14. The method of claim 11, wherein the displacementdevice is configured to displace at least one mirror at an angle to thebeam axis of the collimated laser beam and/or transversely to thedirection of deflection of the partial beam of the collimated laserbeam.
 15. The method of claim 11, wherein the power ratio betweenreflected and non-reflected collimated laser beam can be set or adjustedby the displacement device by changing the dimension of the area of thereflecting surface of one of the shifted mirrors in the collimated laserbeam.